A Phase-Field Regularized Cohesion Model for Hydrogen-Assisted Cracking

Abstract

Hydrogen-assisted cracking (HAC) usually causes premature mechanical failure of the material and results in structural damage in hydrogen environments. A phase-field regularized cohesion model (PF-CZM) was proposed to address hydrogen-assisted cracking. It incorporated the hydrogen-enhanced decohesion mechanism to decrease the critical energy release rate to address damage initiation and progression in a chemo-mechanical coupled environment. This model is based on coupled mechanical and hydrogen diffusion responses, driven by chemical potential gradients, and the introduction of hydrogen-related fracture energy degradation laws. The coupling problem is solved by an implicit time integral, in which hydrogen concentration, displacement and phase-field order parameters are the main variables. Three commonly used loading regimes (tension, shear, and three-point bending) were provided for comparing crack growth. Specifically, (i) hydrogen-dependent fracture energy degradation, (ii) mechanical–chemical coupling, and (iii) the diffusion coefficient D is influenced by both the phase field and the chemical field. By considering these factors, the PF-CZM model provided a variational framework by coupling mechanical loading with concentration diffusion for studying the complex interplay between a chemo-mechanical coupled environment and material damage, thereby enhancing our understanding of hydrogen-assisted cracking phenomena.